On-load voltage regulators

ABSTRACT

An on-load voltage regulator comprises a transformer having a magnetic core, a primary winding on the core, and a rotatable secondary winding in the form of a bare wire conductor coiled helically around the core. A brush cooperates with the second winding and is movable axially but not angularly relative to the secondary winding. A slip ring connector at one end of the secondary winding has fixed elements and an element which bridges the fixed elements and which is connected to the end of the secondary winding and is rotatable therewith. An inverse potential is applied between the fixed elements for the purpose of maintaining the potential between the fixed elements at a zero value in use when they are bridged by the rotatable element of the slip ring connector.

United States Patent w13,ss1,1s9

3,211,956 10/1965 Dombush lnventor Maurice Sinet 45 Blvd. Stalingrad 92, Antony, France Appl. No. 838,615 Filed July 2, 1969 Patented May 25, 1971 Priority July 3, 1968 France 157,661

ON-LOAD VOLTAGE REGULATORS 6 Claims, 4 Drawing Figs.

US. Cl 323/43.5R, 323/47, 323/51 lnt. Cl. ..H0lt 29/04, H02p 13/06 Field of Search 323/44, 45, 46.47, 5l53, 43.5;317/14, 15,16

References Cited 5 UNITED STATES PATENTS 3,505,591 4/1970 Scott ABSTRACT: An on-load voltage regulator comprises a transformer having a magnetic core, a primary winding on the core, and a rotatable secondary winding in the form of a bare wire conductor coiled helically' around the core. A brush cooperates with the second winding and is movable axially but not angularly relative to the secondary winding. A slip ring connector at one end of the secondary winding has fixed elements and an element which bridges the fixed elements and which is connected to the end of the secondary winding and is rotatable therewith. An inverse potential is applied between the fixed elements for the purposeof maintaining the potential between the fixed elements at a zero value in use when they are bridged by the rotatable element of the slip ring connec AAA LOAD

' P'ATENTED mesmn 3 581 189 V SHEET 1 OF 2 PATENTED was I97: 3581; 189

sum 2 0F 2 N 4 3 LOAD 25 25 27 M/lUR/CE S/zver ON-LOAD VOLTAGE REGULATORS This invention relates to on-load voltage regulators of the transformer type and having a rotating winding.

These transformers are well known and have a secondary winding in the form of a bare wire conductor which is coiled helically and with which a brush cooperates. This brush, when the winding is rotating, is constrained to move axially along the winding in a manner to remain in contact with the conductor. The output voltage of the secondary winding is in theory proportional to the number of turns of the winding in circuit between the movable brush and the other end of the winding. There are no .practical problems in taking current at the movable brush, but this is not the case at the said one end of the winding. In practice, taking current at the end of the winding cannot be performed by a brush cooperating with a ring, since the ring would surround the transformer core and would be the seat of a short circuit current. To avoid this short circuit current, it is necessary to split the ring radially; but when the brush passes over the radial gap in the ring, as a voltage difference equal to the voltage induced in one turn exists between the two edges of the gap, an arc is produced and this leads to the destruction of the brush and of the ring. To

remedythis, attempts have been made to reduce the potential between the edges of each gap, by increasing the number of gaps in the ring, but this solution leads to a complex connection which, moreover, necessitates leads passing into the interior of the path of the magnetic flux; in turn this necessitates the magnetic core being split by longitudinal gaps.

An.object of this invention is to provide an on-load regulator of the transformer type in which the stated problem is at least alleviated.

Embodiments of this invention will now be described by way of example only, with reference to the accompanying schematic drawing, in which:

FIG. 1 is a simplified circuit diagram of an on-load regulator in accordance with this invention;

FIG. 2 is a circuit diagram of one embodiment of this invention having a rotatable semiring and two fixed brushes;

FIG. 3 is a circuit diagram of another embodiment of this invention which utilizes the saturation of transformers in opposition; and

FIG. 4 is a perspective schematic view of a regulator embodying the circuit of FIG. 1.

Referring to FIG. 1, reference numeral I denotes the magnetic core of the main transformer; 2 denotes two fixed collector semirings at the end of secondary winding 3a and 3b denote gaps between the fixed semirings 2; and 4 denotes a brush which cooperates with the semirings 2. Reference numeral 5 denotes the secondary winding of an auxiliary transformer 6, the secondary winding 5 being connected to the two semirings 2. The output terminal of the current is a center tap 7 of the secondary winding 5. Numeral 8 denotes the primary winding of the transformer 6. As the two semirings 2 are not in contact with each other, they cannot, in any eventuality and whatever may be the position of the brush 4, be the seat of an electromotive force. When the brush 4 bridges the gap 30, the magnetic flux passing through the core I does not pass through the closed circuit constituted by the semirings 2 and the secondary winding 5 of the transformer 6, and consequently there is no electromotive force induced between the two ends of the gap 30. On the other hand, when the brush 4 bridges the gap 3b, the closed circuit constituted by the semirings 2 and the winding 5 has the charging flux in the core 1 passing through it and an electromotive force proportional to this flux is induced in this closed circuit. To prevent the induction of this e.m.f. so as to avoid the formation of an electric arc, an electromotive force of the opposite sense is induced in the secondary winding 5 of the transformer 6, by appropriately energizing the primary winding 8 of the transformer 6.

In the embodiment shown in FIG. 2, numeral 1 denotes the magnetic core but all other components have reference numerals other than those shown in FIG. 1. The fixed semirings and rotatable brush of FIG. 1 are omitted and, instead, a collector semiring 9 is connected at 10 to the end of the secondary winding of the main transformer, and is caused to rotate with the rotatable secondary winding. The semiring 9 cooperates with two fixed opposed brushes 11 which are connected to the ends of respective secondary windings 12 of auxiliary transformers 13. The other ends of the windings 12 are connected to a current output terminal 14. As in the arrangement shown in FIG. I, when the semiring 9 is in contact with only one of the brushes 11, or when it is in contact with both brushes 11 in such a manner that the magnetic flux in the core I does not pass through the closed circuit comprising the semiring 9, the brushes 1] and the secondary windings 12, of the auxiliary transformers 13, no electromotive force is in duced in this closed circuit. On the other hand, in the position of the semiring 9 shown, an electromotive force is induced in the stated closed circuit and this e.m.f. would produce an are at the moment of closing and of breaking of the closed circuit. To avoid this inconvenience, an inverse electromotive force is induced in the secondary windings 12 of the auxiliary transformers 13. For this purpose, the primary windings 15 of the transformers 13 are connected in series between a fixed brush l6 and a movable brush 17 of an auxiliary annular transformer 18. In this transformer, the two semiannular portions A and B are energized in parallel, the windings of these two portions being wound in opposite directions. The movable brush 17 is driven in synchronism with the rotatable winding of the main transformer and the semiring 9 to give a maximum electromotive force when the semiring 9 is in the position shown and a zero force when it is in the opposite position.

In the embodiment shown in FIG. 3, the output of the annular transformer 18 is applied to the primary windings 15 of the transformers 13 as in FIG. 2. In this embodiment, the end of the rotatable secondary winding is connected to a rotatable brush 4 which cooperates fixed semirings 2 as described with reference to FIG. I, the same elements bearing the same reference numerals in FIGS. 1 and 3. Nevertheless, when the supply voltage of the primary windings 15 of the transformers I3 is zero, the terminals of the primary windings are the seat of a self current under the influence of the current flowing through the secondary windings 12. To remedy this, the transformers 13 are saturated, the saturation of the primary windings 15 being effected by-a transformer 19. The primary winding 20 of the transformer 19 is connected between the rotatable brush l7 and the terminal 21 of the annular transformer 18 to which the maximum potential is applied. The secondary winding 22 of this transformer 19 supplies two saturation windings 23 connected in such a manner as to ensure the saturation of the transformers 13 without inducing electromotive forces in the terms of the other windings.

FIG. 4 is a schematic view of an on-load regulator of the well known transformer type including the circuit diagram of FIG. 1.

On load regulators of the transformer type are well known in the art and are described e.g. in French Pat. Nos. 1,083,128, 1,158,424, 1,201,946 and 1,244,102.

They comprise with reference to FIG. 4 a magnetic core 1, a primary winding 25 fed by an AC source 26, a secondary winding 27 surrounding an arm of the magnetic core said winding being bare wire coiled on a nonmagnetic cylinder 28 rotatable by a motor M, a sliding'brush 29 movable along the bare wire of the secondary winding and a rotary brush 4 at one end of the secondary winding cooperating with a fixed ring or with fixed half rings 2 the load being connected between the fixed ring or half rings 2 and the sliding brush 29. The voltage applied to the load is proportional to the number of turns of the winding in circuit between the sliding brush 29 and the rotary brush 4.

The embodiments described above may be modified in various ways. For example the variable supply source provided by the transformers 13 could be of any tube and could be constituted by an auto-transformer or a thyristor.

. Having described my invention, I claim:

1. An on-load voltage regulator comprising a transformer having a magnetic core, a primary winding wound on the core, and a secondary winding consisting of a bare wire conductor which is coiled helically around the core, the secondary winding being rotatable, a brush which cooperates with the secondary winding and is movable axially but not angularly in relation to the secondary winding, a slip ring connector at one end of the secondary winding, the slip ring connector having fixed elements and an element which bridges said fixed elements and which is connected to the end of the secondary winding and is rotatable therewith, and means for applying between the fixed elements of the slip ring connector a potential such that, in use, the potential between those fixed elements is zero when they are bridged by said rotatable element of the slip ring connector.

2. An on-load voltage regulator as claimed in claim I, wherein the slip ring connector comprises a fixed ring split into two segments and a rotatable brush, the said potential being applied, in use, between the segments of the fixed ring.

3. An on-load voltage regulator as claimed in claim I, wherein the slip ring connector comprises tow fixed brushes and a rotatable part ring, the said potential being applied, in use, between the fixed brushes.

4. An on-load voltage regulator as claimed in claim 1, wherein the said potential applying means comprises auxiliary transformers arranged to supply the said potential.

5. An on-load regulator as claimed in claim 4, wherein the auxiliary transformers are arranged to be saturated when the potential to be applied to the fixed elements of the slip ring connector is zero.

6. An on-load voltage regulator as claimed in claim 4, wherein the auxiliary transformers are arranged to be energized by the annular transformer having a tapping on its secondary winding mounted for rotation together with the secondary winding on said magnetic core of the transformer. 

1. An on-load voltage regulator comprising a transformer having a magnetic core, a primary winding wound on the core, and a secondary winding consisting of a bare wire conductor which is coiled helically around the core, the secondary winding being rotatable, a brush which cooperates with the secondary winding and is movable axially but not angularly in relation to the secondary winding, a slip ring connector at one end of the secondary winding, the slip ring connector having fixed elements and an element which bridges said fixed elements and which is connected to the end of the secondary winding and is rotatable therewith, and means for applying between the fixed elements of the slip ring connector a potential such that, in use, the potential between those fixed elements is zero when they are bridged by said rotatable element of the slip ring connector.
 2. An on-load voltage regulator as claimed in claim 1, wherein the slip ring connector comprises a fixed ring split into two segments and a rotatable brush, the said potential being applied, in use, between the segments of the fixed ring.
 3. An on-load voltage regulator as claimed in claim 1, wherein the slip ring connector comprises tow fixed brushes and a rotatable part ring, the said potential being applied, in use, between the fixed brushes.
 4. An on-load voltage regulator as claimed in claim 1, wherein the said potential applying means comprises auxiliary transformers arranged to supply the said potential.
 5. An on-load regulator as claimed in claim 4, wherein the auxiliary transformers are arranged to be saturated when the potential to be applied to the fixed elements of the slip ring connector is zero.
 6. An on-load voltage regulator as claimed in claim 4, wherein the auxiliary transformers are arranged to be energized by the annular transformer having a tapping on its secondary winding mounted for rotation together with the secondary winding on said magnetic core of the transformer. 